So!, we already have Dynamics AX 2009 RTM version!! (It was released yesterday, May 22nd).
It is AVAILABLE NOW for download from Partner Source (you need to authenticate as a Dynamics partner):
The download is a full installation setup, either for new installations or upgrades from previous versions.
You can upgrade it from Microsoft Dynamics AX 3.0 Service Pack 4 (or higher) or Microsoft Dynamics AX 4.0 Service Pack 1 (or higher).
AX 2009 is gonna rock!